<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    function getSum(n = 0, m = 0) {
      let sum = 0
      for (let i = n; i <= m; i++) {
        sum += i
      }
      document.write(sum)
    }
    // getSum()
    let num1 = +prompt('请输入第一个数：')
    let num2 = +prompt('请输入第二个数：')
    getSum(num1,num2)
  </script>
</body>
</html>